Windows 7 PC can't see iMac

Sharing, SMB, all that stuff is enabled on my iMac. The Windows 7 PC can see my iMac in "Network Neighborhood", but when I double-click on my iMac it fails to login -- doesn't like username or password, presumably.

The iMac can see the Windows 7 PC and can log into individual user accounts on it, perform file transfers, etc. Just not the other way around. 😟

The iMac's computer name is "iMac" and the username is "Larry". The Windows 7 PC pre-fills the login username as "\iMac\Larry" and from what I've scanned in these forums, that's supposed to work. But it does not.

If I choose the "login with other user name" option in the Windows 7 dialog box, I can type in any username but nothing works -- just "Larry", "\\iMac\Larry", etc., etc.

What am I missing? This used to be so simple.

Thx...